Thank you for the comments! It is indeed going to be used in a game (which I hope my friend will actually finish, lol). I use the music tracking program OpenMPT, which is mostly-sample-based, so I actually use samples (WAV) for all the chip sounds.

The only thing you really need to make a good chiptune is good, clean chip samples. These samples are incredibly short, so you can't play them by themselves. They need to loop.

For the percussion, I usually get some actual NES or Mega drive samples. Those are already the real deal, after all, and need no editing. You could also downsample more realistic percussion sounds (OpenMPT has a special button for this). The sample will lose a bit of the high range sounds, so it sounds a lot more as if the sample was played on a bad sound card. Downsample enough and it becomes very 8-bit like (if it doesn't become useless, which sometimes happens too).

I've never done it, but sound engineering tools like Audacity let you play around with sound filters so much you can probably make most samples sound as if they come from an 8-bit console.

Here's a small collection of samples that I use: davince.tengudev.com/music/oth ers/samples/some-chipsamples.rar

It doesn't contain all of the samples from this specific song, though. Just one or two of it are used in my song. But that pack is complete enough to get you started making very NES/GB-like songs at least.

...Alternatively to all this samples stuff, you can use tools like Famitracker, which is music creation software that lets you make tunes for the actual consoles themselves. Famitracker is for NES, but there are also music trackers for Commodore 64, Gameboy, etc etc. The songs made in these sound exactly like they come from that console. However, this also limits you to the actual original console hardware's capabilities. People have made great tunes with those, they can play on an actual NES, but they can't have as many simultaneous instruments or freedom in how the instruments sound as when you use samples in your favourite music creation program (like I like to do).